Abstract: A novel energy-dissipation brace with a notched thick-walled steel tube (EDB-NTWST) was proposed to solve the problems of complex connections or unexpected damage in existing metal energy-dissipating devices. The EDB-NTWST was designed to dissipate energy through a notched thick-walled steel tube (NTWST), which was proposed for the first time. Only the damaged NTWSTs need to be replaced rather than the entire brace after a major earthquake, which is beneficial for rapid post-earthquake restoration. Two structural configurations of the EDB-NTWST were presented based on different configurations of the NTWST. A simplified mechanical analysis method for the NTWST was derived. The accuracy of the theoretical analysis and numerical simulation was verified by experimental investigation. The parametric study on 16 NTWST specimens based on finite element analysis was conducted under monotonic and cyclic loads. The results show that the EDB-NTWST exhibits full hysteresis curve, excellent deformation capacity and high ductility. In addition, the damage is concentrated on the NTWST and the goal of reusability is achieved. The analytical prediction and experimental data agree well with each other. This indicates that the simplified mechanical analysis method is reliable and can be applied to the preliminary design of EDB-NTWSTs. The mechanical properties of NTWSTs can be adjusted by changing their design parameters. For instance, the thickness of the energy-dissipation ring can be increased to enhance the bearing capacity, while increasing the number of energy-dissipation rings can significantly improve the deformation capacity. Additionally, widening the energy-dissipation ring and reducing its middle diameter are effective for enhancing the ductility of NTWST.